Upgrading PitStop Server to 2018 can be a big PITA depending on how your current setup is and how well documented your flows are. This due to the fact that PitStop Server handles action lists/preflight profiles a bit differently.

I had used Select from Folder and put all of my actions/preflights in a separate folder which meant that after the upgrade PitStop couldn't find and actions/preflights. I did however find a way to find out which action/preflight was linked to a specific configurator by selecting Define multi-line text with variables which showed me which action/preflight was used.

Also I imported all actions/preflights into PitStop Server 2018 and added them via Select many from Library... instead.

If you build a path to an action/preflight you used to have a path like /Users/Username...., but now you need to use //Users/username.

PitStop 2018 has some new features, but if you don't need them I think you can stay with 2013 for now.

I think it may help to have all actions/preflight profiles imported to PitStop Server and selected from library before upgrade, but it may still be a problem. I had a bit of fun figuring out which action lists I had used in a particular configurator before I found part of the name by checking Define multi-line text with variables.
The best thing would most likely be to make a note of which action list/preflight profiles was used in each configurator before you upgrade PitStop Server though, as that may come in handy.
Other than this it should be smooth sailing...